Repetitive Control for Single Link Flexible Manipulators

This paper proposes a new method for effective control of single link flexible manipulators. Dynamic models of these arms are complex because their mass is distributed along the link. Then control systems of these arms are usually complicate because they include complex observers, or some kind of inversion of these high order dynamics. We propose here a simple controller for these arms, based on a relatively new control technique called repetitive control. In order to apply this technique here, the dynamics of the arm has to be modified in such way that all the vibration modes have to be multiple of a basic frequency. This can be easily achieved by attaching some small masses at some points of the link. After repetitive control may be applied. The resulting controller is very simple, it is easy to tune, and only needs feedback of two signals: motor angle and torque measured by a strain gauge placed on the base of the arm. Simulations carried on a standard flexible arm show the effectiveness of our method.